1. Technical Field
The present invention relates to the field of protecting copyrighted works from piracy by fingerprinting or watermarking the copyrighted information and, more particularly, to a method and apparatus for inserting hidden data such as a digital watermark into a signal representing a copyrighted work simultaneously with or immediately after 1) perceptually encoding a digital representation of an audio signal or 2) perceptually or otherwise coding a digital representation of a video signal or other information carrying signal.
2. Description of the Related Arts
Piracy of copyrighted works is a serious problem. By way of example, street vendors in metropolitan areas offer videotapes, audio compact discs, audio tapes and the like which appear on their surface to have been properly distributed and offered for sale with the permission of or under license to the copyright owner, when, in fact, they are not. Computer software and games are distributed freely via the Internet and pirate copies abound. There are many ways a pirate can obtain free access to a copyrighted work that is original. By "original" as intended herein, we define "original" as an original or master copy from which other copyright owner authorized copies have been made or an "original" is an authorized copy made from the original or master copy. All other copies will be defined herein as "pirate" copies and comprise copies that are not authorized by a copyright owner.
By way of example of the ease with which a pirate is able to make a pirate copy, the pirate can produce a high quality, perhaps, perfect reproduction from an original that they have legitimately purchased or otherwise legitimately obtained, can record a live performance for which copyright protection is asserted or can record from a broadcast performance of a live or copied performance. Other means of pirating are best known to the pirates themselves.
It is an objective of the present invention to protect a copyrighted work. Protection methods are known. Despite efforts by pirates to make a copyrighted work appear to be an original, a method is known to attempt to hide in the copyrighted work itself indicia of the copyright owner's identity and source. The burying of such indicia perhaps began with early map-makers who would "fingerprint" their work by intentionally placing an error in the map. The map maker could quickly look at a copy, recognize their fingerprint (intentional error) and then accuse the individual offering the map of infringement, knowing the offeror to not be authorized to do so. Today, it is known to embed in integrated circuits a fingerprint or indicia of ownership that may appear on the surface to comprise a circuit component, when in fact, the indicia comprises a fingerprint intended by the owner to deceive a pirate.
With works created on paper, it is known to "watermark" the paper itself with indicia of its source. For example, since the mid-1800's, it became known and desirable to protect the authenticity of such items of value as postage stamps and currency from copying/counterfeiting by watermarking the item of value. A watermarked item of value or legal document can both identify and verify the source of the document.
As used herein, by fingerprinting and watermarking, no distinction is intended between them regardless of their historical distinctions. Watermarking as used herein is intended to refer to either term and to signify the same process; namely, it is an objective of watermarking to identify and to verify the source of an original as defined above.
According to the prior art, it is not only known to use watermarking for works created on paper but also for protecting analog or digital signals representative of a copyrighted work. For example, in binary digital bitstreams for transmitting digital audio signals in a cable television system, it is known to identify, for example, the title, track and artist in a header portion of blocks of data representative of a copyrighted work. The problem with such systems is that the location of the header carrying such a watermark can be easily become known to a would-be pirate. It always appears at the beginning of the work. Consequently, the watermark can be easily removed.
Digimark Corporation of Portland, Oregon offers a method of watermarking images that may represent copyrighted works. In particular, pixels within digital photographic images carry a digital watermark prior to distribution of the images, for example, over the Internet. By hiding the watermark within the image itself, it is expected that a pirate will have difficulty locating the watermark. Consequently, it is a further objective of the present invention to not only apply a watermark but apply a watermark in such a manner as to disguise its location from a pirate so the pirate cannot simply remove it.
In the art of coding copyrighted works, there has been a recent movement toward perceptual coding. Perceptual coding relates to coding and decoding designed to recognize that the signal fidelity perceived by humans is a better quality measure than "fidelity" computed by traditional distortion measures. Traditionally, for example, it might be a measure of quality to assert that a speaker has a flat frequency response across the spectrum of frequencies between 0 frequency and 20,000 Hertz. On the other hand, the human ear may not be able to even hear frequencies at the lower or higher end of the spectrum. Now, for example, in audio, quality is defined to mean "listener indistinguishable from compact disc audio," generally regarded today as the best quality audio in comparison with tape, record or earlier forms of recording a live performance.
Patents describing audio perceptual coding include U.S. Pat. No. 5,285,498 of Johnston issued in 1994. FIGS. 1 and 2 of the '498 patent generally describe prior art perceptual coders, typically involving the conversion of analog data to digital, a transformation of the digital data in association with a perceptual model and a quantizer. Recent articles on perceptual encoding/decoding include: "AT&T Perceptual Audio Coding (PAC)" of Johnston et al., Collected Papers on Digital Audio Bit-Rate Reduction, Feb. 13, 1996 and the following three papers "MPEG-2 Audio Stereo and Multichannel Coding Methods" by Johnston et al.; "ISO/IEC MPEG-@ Advanced Audio Coding" by Bosi et al.; and "Enhancing the Performance of Perceptual Audio Coders by Using Temporal Noise Shaping (TNS)" by Herre et al., all published with Conference Papers of the 101.sup.st Convention of the Audio Engineering Society, November 8-11, 1996. The recent papers describe alternative embodiments and enhancements to the original perceptual coding apparatus and methods described, for example, by Johnston in the '498 patent and his predecessors. Recently filed patent applications on related subject matter incorporated by reference herein include U.S. Pat. No. 6,111,844, issued Aug. 29, 2000 entitled "Quality Degradation Through Compression/Decompression" and U.S. application Ser. No. 08/888,014 entitled "Custom Character Coding Compression for Encoding and Watermarking Media Content," mailed Jul. 3, 1997. Also, this application claims priority to U.S. provisional application Ser. No. 60/067,225 filed Dec. 3, 1997 entitled "On Combining Watermarking with Perceptual Coding." This application, converted to a regular application, has been published as WO99/29114 on Jun. 10, 1999.
By perceptual coder as used herein is intended a general form of coder which may comprise simple perceptual coders or more complex perceptual coders, for example, hybrid coders, integrated source-model perceptual coders and perceptual coders using temporal noise shaping among other coders.
Information carrying signals that have high information content do not appear to be susceptible to elimination of "irrelevance" and perceptual coding. For example, a digital data computer program may have an undiscovered and so not particularly "relevant" embedded subroutine. Nevertheless, compression principles may still be applied to such a signal to eliminate redundancy. Yet, perceptual coding may be applied to such a signal for at least the latter reason.
The ability to easily replicate digital audio, video, computer program, game and other data, protectable by copyright, by simply copying binary bitstreams is a major impediment to the use of the Internet or other telecommunications channels for content distribution/sale. Consequently, it is a further objective of the present invention to eliminate such an impediment to commerce over the "information superhighways" of the future.
Thus, in view of the above, it is an object of the present invention to provide apparatus and a method of watermarking a video television signal as well as an audio or other information carrying signal and open up the information superhighway to free commerce in protected data.